1. Field of the Invention
The present invention relates to a vibration-isolating optical system having a so-called vibration isolating function capable of optically compensating blurring of a photographed image due to vibrations. More particularly, the present invention relates to a vibration-isolating optical system capable of compensating image blurring due to the shaking of the camera when an image is photographed through the imaging optical system and also of compensating image blurring when an image to photographed by the imaging optical system loaded on a portion such as an automobile or a helicopter which is being vibrated.
2. Related Background Art
Hitherto, a system of the type capable of optically compensating image blurring has been known as disclosed in (1) Japanese Patent Publication No. 56-23125 in which it is employed in an automatic vertical optical device. According to this disclosure, the optical axis is vertically compensated by causing a prism effect to be changed by relatively rotating the positive and negative lenses in an optical system along the interacting lens surfaces. Another system has been disclosed in (2)
Patent Publication No. 41-8558 in which the nodal Japanese point is shifted and the image formation point is thereby compensated by causing a portion of the lenses in the optical system to be eccentric with respect to the optical axis.
However, the structure disclosed in the above-described Japanese Patent Publication (1) encounters a problem in the deterioration in the imaging performance because the aberration excessively deteriorates when the positive lens and the negative lens have been made eccentric to each other and the aberration change is too large to serve as an ordinary imaging optical system. As a result, it has not been put into practical use as a satisfactory imaging optical system. According to the above-described Japanese Patent Publication (2), only the principal structure was disclosed and there has not been a description of the aberration compensation to be made at the time of compensating the eccentricity.
Another structure has been disclosed in, for example, Japanese Patent Laid-Open No. 63-201623 in which the aberration when the eccentric state has been realized is compensated to some extent by using the principle disclosed in the above-described Japanese Patent Publication (2).
However, the structure disclosed in it suffers from a problem in that the substantial overall length of the eccentricity-compensating optical system is too great and the compensating optical system and that of the holding mechanism therefor thereby become too heavy. As a result, the actuator for operating the compensating optical system and the holding mechanism therefor is heavily loaded.